JPS6314057B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Background of the Invention Traditionally, aluminum alloys have been used in engine blocks of internal combustion engines because of their light weight. To provide the cylinder bore with the necessary wear resistance, it was common to chrome plate the cylinder bore or to cast an iron liner into the cylinder bore. It is difficult to plate cylinder bores uniformly, and plating is an expensive operation. When using a cast iron liner,
The overall cost of the engine block increases as well as the engine weight.

Hypereutectic aluminum-silicon alloys containing 17-19% silicon by weight have good wear resistance due to the precipitated silicon crystals that form the main phase. Because of this wear resistance, attempts have been made to utilize hypereutectic aluminum-silicon alloys as casting alloys for engine blocks to eliminate the need to plate cylinder bores or cast liners.

The silicon content of aluminum/silicon/copper alloys is 17~
It has been found that increases to the range of 19% have an adverse effect on the castability of ternary alloys. For example, 16
~18% silicon, 0.6-1.1% iron, 4.0-5.0% copper,
0.1% manganese, 0.45-0.65% magnesium,
Common hypereutectic aluminum-silicon-copper alloys containing residual aluminum have good wear resistance, desirable low solids fractionation at eutectic temperatures, and exhibit good flow properties. However, this alloy
It has a wide solidification temperature range of around 250 degrees, and its castability is extremely low. Additionally, this alloy contains significant amounts of copper, which makes it less resistant to corrosion in saltwater environments, making it unsuitable for use in marine engines.

Another commonly used hypereutectic aluminum-silicon alloy has a nominal composition of 19% silicon, 0.6% copper, 1% magnesium, 0.4% manganese, and the balance aluminum. Again, this alloy exhibits good wear resistance due to its precipitated silicon crystals, but relatively poor corrosion resistance in saltwater environments.

SUMMARY OF THE INVENTION The present invention is directed to an improved hypereutectic aluminum-silicon casting alloy that can be used to cast engine blocks for marine engines.

The alloy of the present invention contains 16-19% by weight silicon and 0.4-19% by weight silicon.
Contains 0.7% by weight of magnesium, up to 1.4% by weight of iron, up to 0.3% by weight of manganese, up to 0.37% by weight of copper, and the balance aluminum. The copper content is kept as low as possible, preferably 0.37% or less.

Due to the precipitated silicon crystals, this alloy has excellent wear resistance.

Because the copper content is kept to a minimum, the salt water corrosion resistance of the alloy is greatly improved, making it particularly useful as a casting block for marine engines.

By suppressing the copper content, the three-element aluminum-silicon-copper eutectic was avoided, which was completely unexpected, but it was less than 150〓, preferably 100〓.
The following relatively narrow coagulation range can be obtained: These properties are the result of three-element hypereutectic aluminum.
Significantly improves the castability of silicon alloys.

Other objects and advantages will become apparent from the description below.

DESCRIPTION OF PREFERRED EMBODIMENTS The hypereutectic aluminum-silicon casting alloy of the present invention has the following approximate composition in weight percent.

Silicon 16-19% Magnesium 0.4-0.7% Iron up to 1.4% Manganese up to 0.3% Copper up to 0.37% Aluminum Balance Magnesium acts to strengthen the alloy,
Iron and manganese tend to increase the alloying degree, lower its coefficient of thermal expansion, increase its machinability, help maintain mechanical properties at high temperatures, and increase its solder resistance in die casting applications.

Copper content is kept below 0.37%, preferably kept to a minimum. By significantly reducing the copper concentration, the corrosion resistance of the alloy in chlorinated environments is significantly improved, making the alloy particularly useful in engine blocks and other parts of marine engines requiring strength, wear resistance, and corrosion resistance. Become. This alloy is 5%
There is less than 1% weight loss when exposed to sodium chloride solution for 200 hours.

The alloy may also contain small amounts of residual hardening elements, up to 0.2% each, such as nickel, chromium, zinc or titanium.

This alloy has excellent wear resistance and has excellent fluidity due to the silicon component mentioned above.

Since the copper content is minimized, the aluminum-silicon-copper eutectic is correspondingly eliminated, so that the solidification range of the alloy is relatively narrow, less than 150〓, preferably less than 100〓. .

These properties of good flowability and narrow solidification range provide an alloy with improved castability over known hypereutectic ternary aluminum-silicon casting alloys.

Furthermore, the alloy of the present invention has an ultimate tensile strength of 20,000 to 35,000 psi, a yield strength of 15,000 to 30,000 psi,
and an elongation percentage of 0-2%.

Upon cooling from solution, silicon precipitates relatively large crystals. However, when casting a block using a metal core, there is an area bordering each cylinder bore that is devoid of silicon crystals due to the rapid dissipation of heat into the metal core. Under normal slow cooling, this region has a thickness of about 0.02 inches, while under rapid cooling conditions this region can be up to 0.05 inches thick. Due to the lack of silicon crystals, the wear resistance in this area is low. Conventionally, it has been common practice to perform extensive machining to expose the silicon crystal on the cylinder bore surface to remove this area lacking silicon crystal.

However, when engine blocks are cast from the alloy of the present invention, it has been found that dry sand or salt cores eliminate the areas lacking silicon crystals. Such a core retards the transfer of heat from the molten alloy, allowing the casting to cool at a relatively slow rate. In this case, the silicon crystals spread over the surface of the cylinder bore, eliminating the need for extensive machining and considerably reducing the manufacturing costs of the engine block.

In the following, specific examples of alloys according to the invention are presented together with their mechanical properties.

Example Alloy composition (wt%) Silicon 16.90 iron 0.92 Copper 0.14 Manganese 0.12 Magnesium 0.41 Aluminum 81.51 Coagulation range 79〓 corrosion weight loss (200 hours in 5% NaCl solution) 0.18% Ultimate tensile strength 31157psi Yield strength 31157psi Elongation percentage 0 Example Alloy composition (wt%) Silicon 16.80 iron 1.03 Copper 0.33 Manganese 0.18 Magnesium 0.50 Aluminum 81.16 Coagulation range 86〓 corrosion weight loss (200 hours in 5% NaCl solution) 0.49% Ultimate tensile strength 29164psi Yield strength 29164psi Elongation percentage 0

Claims (1)

Claims: 1. A component for an internal combustion engine, comprising a casting of a hypereutectic aluminum-silicon alloy, which alloy consists essentially of 16-19% by weight of silicon and 0.4% by weight of silicon.
~0.7 wt% magnesium, up to 1.4 wt% iron, up to 0.3 wt% manganese, and 0.37 wt%
Component consisting of up to 100% of copper and the remaining aluminum, characterized in that this alloy has excellent flow properties and a solidification range of less than 150%. 2. A component according to claim 1, characterized in that the casting is uniformly distributed and contains silicon crystals. 3. A component according to claim 1, characterized in that the alloy has an ultimate tensile strength of 20,000 to 35,000 psi, a yield strength of 15,000 to 30,000 psi, and a percent elongation of 0 to 2%. Component part. 4. The component according to claim 1, wherein the component is an engine block having at least one cylinder bore, and when the block is cast, the entire block including the area bordering each of the cylinder bores is A component characterized in that it contains uniformly distributed precipitated silicon crystals. 5. A component according to claim 1, characterized in that the casting has a weight loss of less than 1.0% when exposed to a 5% sodium chloride solution for 200 hours at ambient temperature. 6. A method of casting an engine block, comprising:
forming a mold having a plurality of non-metallic cores configured and arranged to form cylinder bores in a cast engine block, and comprising essentially 16-19% by weight silicon and 0.4-0.7% by weight magnesium; up to 1.4% iron and up to 0.3% manganese,
Consisting of up to 0.37% copper by weight and the balance aluminum, it has a solidification range of less than 150% and has a solidification range of less than 200% at ambient temperature.
creating a hypereutectic aluminum-silicon alloy that has a weight loss of less than 1% when exposed to a 5% sodium chloride solution for an hour; pouring the alloy into a mold and contacting the core; cooling the cast alloy to produce a solidified cast engine block having precipitated silicon crystals substantially uniformly distributed throughout.